Detecting media defects

ABSTRACT

A computer program product, according to one embodiment, includes a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a controller to cause the controller to: monitor, by the controller, a resistance value of each of a plurality of detector structures positioned in an array, and detect, by the controller, a change in a resistance value of at least one of the detector structures, for identifying a defect on a magnetic medium. Each of the detector structures includes a pair of conductive layers separated by an insulating material. Moreover, none of the detector structures include an operable reader for reading data from a magnetic medium. Other systems, methods, and computer program products are described in additional embodiments.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to detecting defects on magnetictape media.

In magnetic storage systems, magnetic transducers read data from andwrite data onto magnetic recording media. Data is written on themagnetic recording media by moving a magnetic recording transducer to aposition over the media where the data is to be stored. The magneticrecording transducer then generates a magnetic field, which encodes thedata into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magneticfield of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

In a tape drive system, the drive moves the magnetic tape over thesurface of the tape head at high speed. Usually the tape head isdesigned to minimize the spacing between the head and the tape. Thespacing between the magnetic head and the magnetic tape is crucial;therefore, such systems attempt to position the recording gaps of thetransducers, which are the source of the magnetic recording flux, innear contact with the tape to effect sharp written transitions, and toposition the read elements in near contact with the tape to provideeffective coupling of the magnetic field from the tape to the readelements.

Magnetic tape media sometimes has defects that protrude from the surfaceof the magnetic tape media. In tape recording, the media runs in contactwith the transducers in the head, thus making the transducerssusceptible to effects of media defects.

SUMMARY

A computer program product, according to one embodiment, includes acomputer readable storage medium having program instructions embodiedtherewith, the program instructions executable by a controller to causethe controller to: monitor, by the controller, a resistance value ofeach of a plurality of detector structures positioned in an array, anddetect, by the controller, a change in a resistance value of at leastone of the detector structures, for identifying a defect on a magneticmedium. Each of the detector structures includes a pair of conductivelayers separated by an insulating material. Moreover, none of thedetector structures include an operable reader for reading data from amagnetic medium.

A computer-implemented method, according to another embodiment,includes: monitoring a resistance value of each of a plurality ofdetector structures positioned in an array, and detecting a change in aresistance value of at least one of the detector structures foridentifying an approximate location of a defect on a magnetic medium.Each of the detector structures includes a pair of conductive layersseparated by an insulating material. Moreover, none of the detectorstructures include an operable reader for reading data from a magneticmedium.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 1B is a schematic diagram of a tape cartridge according to oneembodiment.

FIG. 2 illustrates a side view of a flat-lapped, bi-directional,two-module magnetic tape head according to one embodiment.

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2.

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A.

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 is a partial tape bearing surface view of a magnetic head havinga write-read-write configuration.

FIG. 4 is a partial tape bearing surface view of a magnetic head havinga read-write-read configuration.

FIG. 5 is a side view of a magnetic tape head with three modulesaccording to one embodiment where the modules all generally lie alongabout parallel planes.

FIG. 6 is a side view of a magnetic tape head with three modules in atangent (angled) configuration.

FIG. 7 is a side view of a magnetic tape head with three modules in anoverwrap configuration.

FIG. 8A is a partial top-down view of an apparatus according to oneembodiment.

FIG. 8B is a partial detailed view of the apparatus of FIG. 8A takenfrom circle 8B of FIG. 8A.

FIG. 8C is a partial top-down view of an apparatus according to oneembodiment.

FIG. 8D is a partial top-down view of an apparatus according to oneembodiment.

FIG. 8E is a partial top-down view of an apparatus according to oneembodiment.

FIG. 8F is a partial top-down view of an apparatus according to oneembodiment.

FIG. 9A is a partial top-down view of an apparatus according to oneembodiment.

FIG. 9B is a partial top-down view of an apparatus according to oneembodiment.

FIG. 10 is a flowchart of a method according to one embodiment.

FIG. 11A is a partial top-down view of an apparatus according to oneembodiment.

FIG. 11B is a partial cross-sectional view of the apparatus of FIG. 11Ataken along line 11B-11B of FIG. 11A, with a representation of a wiringscheme.

FIG. 11C is a partial cross-sectional view of an apparatus according toone embodiment.

FIG. 11D is a partial cross-sectional view of an apparatus according toone embodiment.

FIG. 12 is a flow diagram of a method according to one embodiment.

FIG. 13 illustrates a detector structure with smeared material thereon.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofsystems that may be able to detect defects and/or determine whether theamount of burnishing performed on a given media meets specifiedrequirements, as well as operation and/or component parts of suchsystems. Thus, some of the embodiments described herein may be able todetermine whether the amount of burnishing performed on the media issufficient to reduce the likelihood of damaging transducers brought intocontact therewith to an acceptable level.

In one general embodiment, an apparatus includes at least one writetransducer, and a plurality of detector structures positioned in anarray. Each of the detector structures includes a pair of conductivelayers separated by an insulating material. None of the detectorstructures include an operable reader for reading data from a magneticmedium.

In another general embodiment, a computer-implemented method includesmonitoring a resistance value of each of a plurality of detectorstructures positioned in an array, and detecting a change in aresistance value of at least one of the detector structures foridentifying a defect on a magnetic medium. Each of the detectorstructures include a pair of conductive layers separated by aninsulating material. None of the detector structures include an operablereader for reading data from a magnetic medium.

In yet another general embodiment, a computer program product includes acomputer readable storage medium having program instructions embodiedtherewith, the program instructions executable by a controller to causethe controller to monitor, by the controller, a resistance value of eachof a plurality of detector structures positioned in an array. Programinstructions are also included to cause the controller to detect, by thecontroller, a change in a resistance value of at least one of thedetector structures, for identifying an approximate location of defecton a magnetic medium, and cause, by the controller, a write transducerto write a signal burst on the magnetic medium in response to detectingthe change in resistance value. Each of the detector structures includesa pair of conductive layers separated by an insulating material. None ofthe detector structures include an operable reader for reading data froma magnetic medium.

FIG. 1A illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1A, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the drive 100.The tape drive, such as that illustrated in FIG. 1A, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller 128 via a cable 130. Thecontroller 128, may be or include a processor and/or any logic forcontrolling any subsystem of the drive 100. For example, the controller128 typically controls head functions such as servo following, datawriting, data reading, etc. The controller 128 may include at least oneservo channel and at least one data channel, each of which include dataflow processing logic configured to process and/or store information tobe written to and/or read from the tape 122. The controller 128 mayoperate under logic known in the art, as well as any logic disclosedherein, and thus may be considered as a processor for any of thedescriptions of tape drives included herein, in various embodiments. Thecontroller 128 may be coupled to a memory 136 of any known type, whichmay store instructions executable by the controller 128. Moreover, thecontroller 128 may be configured and/or programmable to perform orcontrol some or all of the methodology presented herein. Thus, thecontroller 128 may be considered to be configured to perform variousoperations by way of logic programmed into one or more chips, modules,and/or blocks; software, firmware, and/or other instructions beingavailable to one or more processors; etc., and combinations thereof.

The cable 130 may include read/write circuits to transmit data to thehead 126 to be recorded on the tape 122 and to receive data read by thehead 126 from the tape 122. An actuator 132 controls position of thehead 126 relative to the tape 122.

An interface 134 may also be provided for communication between the tapedrive 100 and a host (internal or external) to send and receive the dataand for controlling the operation of the tape drive 100 andcommunicating the status of the tape drive 100 to the host, all as willbe understood by those of skill in the art.

FIG. 1B illustrates an exemplary tape cartridge 150 according to oneembodiment. Such tape cartridge 150 may be used with a system such asthat shown in FIG. 1A. As shown, the tape cartridge 150 includes ahousing 152, a tape 122 in the housing 152, and a nonvolatile memory 156coupled to the housing 152. In some approaches, the nonvolatile memory156 may be embedded inside the housing 152, as shown in FIG. 1B. In moreapproaches, the nonvolatile memory 156 may be attached to the inside oroutside of the housing 152 without modification of the housing 152. Forexample, the nonvolatile memory may be embedded in a self-adhesive label154. In one preferred embodiment, the nonvolatile memory 156 may be aFlash memory device, ROM device, etc., embedded into or coupled to theinside or outside of the tape cartridge 150. The nonvolatile memory isaccessible by the tape drive and the tape operating software (the driversoftware), and/or other device.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of bases 202, each equipped with a module 204, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 3 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B may be made of the sameor similar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 32 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 1024data tracks (not shown). During read/write operations, the readersand/or writers 206 are positioned to specific track positions within oneof the data bands. Outer readers, sometimes called servo readers, readthe servo tracks 210. The servo signals are in turn used to keep thereaders and/or writers 206 aligned with a particular set of tracksduring the read/write operations.

FIG. 2B depicts a plurality of readers and/or writers 206 formed in agap 218 on the module 204 in Circle 2B of FIG. 2A. As shown, the arrayof readers and writers 206 includes, for example, 16 writers 214, 16readers 216 and two servo readers 212, though the number of elements mayvary. Illustrative embodiments include 8, 16, 32, 40, and 64 activereaders and/or writers 206 per array, and alternatively interleaveddesigns having odd numbers of reader or writers such as 17, 25, 33, etc.An illustrative embodiment includes 32 readers per array and/or 32writers per array, where the actual number of transducer elements couldbe greater, e.g., 33, 34, etc. This allows the tape to travel moreslowly, thereby reducing speed-induced tracking and mechanicaldifficulties and/or execute fewer “wraps” to fill or read the tape.While the readers and writers may be arranged in a piggybackconfiguration as shown in FIG. 2B, the readers 216 and writers 214 mayalso be arranged in an interleaved configuration. Alternatively, eacharray of readers and/or writers 206 may be readers or writers only, andthe arrays may contain one or more servo readers 212. As noted byconsidering FIGS. 2 and 2A-B together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complementarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write transducer 214 and the readers, exemplified by the readtransducer 216, are aligned parallel to an intended direction of travelof a tape medium thereacross to form an R/W pair, exemplified by the R/Wpair 222. Note that the intended direction of tape travel is sometimesreferred to herein as the direction of tape travel, and such terms maybe used interchangeably. Such direction of tape travel may be inferredfrom the design of the system, e.g., by examining the guides; observingthe actual direction of tape travel relative to the reference point;etc. Moreover, in a system operable for bi-direction reading and/orwriting, the direction of tape travel in both directions is typicallyparallel and thus both directions may be considered equivalent to eachother.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked MR head assembly 200 includes twothin-film modules 224 and 226 of generally identical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe (−),cobalt zirconium tantalum (CZT) or Al—Fe—Si (Sendust), a sensor 234 forsensing a data track on a magnetic medium, a second shield 238 typicallyof a nickel-iron alloy (e.g., ˜80/20 at % NiFe, also known aspermalloy), first and second writer pole tips 228, 230, and a coil (notshown). The sensor may be of any known type, including those based onMR, GMR, AMR, tunneling magnetoresistance (TMR), etc.

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as ˜45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

The configuration of the tape head 126 according to one embodimentincludes multiple modules, preferably three or more. In awrite-read-write (W-R-W) head, outer modules for writing flank one ormore inner modules for reading. Referring to FIG. 3, depicting a W-R-Wconfiguration, the outer modules 252, 256 each include one or morearrays of writers 260. The inner module 254 of FIG. 3 includes one ormore arrays of readers 258 in a similar configuration. Variations of amulti-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-Rhead, etc. In yet other variations, one or more of the modules may haveread/write pairs of transducers. Moreover, more than three modules maybe present. In further approaches, two outer modules may flank two ormore inner modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. Forsimplicity, a W-R-W head is used primarily herein to exemplifyembodiments of the present invention. One skilled in the art apprisedwith the teachings herein will appreciate how permutations of thepresent invention would apply to configurations other than a W-R-Wconfiguration.

FIG. 5 illustrates a magnetic head 126 according to one embodiment ofthe present invention that includes first, second and third modules 302,304, 306 each having a tape bearing surface 308, 310, 312 respectively,which may be flat, contoured, etc. Note that while the term “tapebearing surface” appears to imply that the surface facing the tape 315is in physical contact with the tape bearing surface, this is notnecessarily the case. Rather, only a portion of the tape may be incontact with the tape bearing surface, constantly or intermittently,with other portions of the tape riding (or “flying”) above the tapebearing surface on a layer of air, sometimes referred to as an “airbearing”. The first module 302 will be referred to as the “leading”module as it is the first module encountered by the tape in a threemodule design for tape moving in the indicated direction. The thirdmodule 306 will be referred to as the “trailing” module. The trailingmodule follows the middle module and is the last module seen by the tapein a three module design. The leading and trailing modules 302, 306 arereferred to collectively as outer modules. Also note that the outermodules 302, 306 will alternate as leading modules, depending on thedirection of travel of the tape 315.

In one embodiment, the tape bearing surfaces 308, 310, 312 of the first,second and third modules 302, 304, 306 lie on about parallel planes(which is meant to include parallel and nearly parallel planes, e.g.,between parallel and tangential as in FIG. 6), and the tape bearingsurface 310 of the second module 304 is above the tape bearing surfaces308, 312 of the first and third modules 302, 306. As described below,this has the effect of creating the desired wrap angle α₂ of the taperelative to the tape bearing surface 310 of the second module 304.

Where the tape bearing surfaces 308, 310, 312 lie along parallel ornearly parallel yet offset planes, intuitively, the tape should peel offof the tape bearing surface 308 of the leading module 302. However, thevacuum created by the skiving edge 318 of the leading module 302 hasbeen found by experimentation to be sufficient to keep the tape adheredto the tape bearing surface 308 of the leading module 302. The trailingedge 320 of the leading module 302 (the end from which the tape leavesthe leading module 302) is the approximate reference point which definesthe wrap angle α₂ over the tape bearing surface 310 of the second module304. The tape stays in close proximity to the tape bearing surface untilclose to the trailing edge 320 of the leading module 302. Accordingly,read and/or write elements 322 may be located near the trailing edges ofthe outer modules 302, 306. These embodiments are particularly adaptedfor write-read-write applications.

A benefit of this and other embodiments described herein is that,because the outer modules 302, 306 are fixed at a determined offset fromthe second module 304, the inner wrap angle α₂ is fixed when the modules302, 304, 306 are coupled together or are otherwise fixed into a head.The inner wrap angle α₂ is approximately tan⁻¹(δ/W) where δ is theheight difference between the planes of the tape bearing surfaces 308,310 and W is the width between the opposing ends of the tape bearingsurfaces 308, 310. An illustrative inner wrap angle α₂ is in a range ofabout 0.3° to about 1.1°, though can be any angle required by thedesign.

Beneficially, the inner wrap angle α₂ on the side of the module 304receiving the tape (leading edge) will be larger than the inner wrapangle α₃ on the trailing edge, as the tape 315 rides above the trailingmodule 306. This difference is generally beneficial as a smaller α₃tends to oppose what has heretofore been a steeper exiting effectivewrap angle.

Note that the tape bearing surfaces 308, 312 of the outer modules 302,306 are positioned to achieve a negative wrap angle at the trailing edge320 of the leading module 302. This is generally beneficial in helpingto reduce friction due to contact with the trailing edge 320, providedthat proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrapangle also reduces flutter and scrubbing damage to the elements on theleading module 302. Further, at the trailing module 306, the tape 315flies over the tape bearing surface 312 so there is virtually no wear onthe elements when tape is moving in this direction. Particularly, thetape 315 entrains air and so will not significantly ride on the tapebearing surface 312 of the third module 306 (some contact may occur).This is permissible, because the leading module 302 is writing while thetrailing module 306 is idle.

Writing and reading functions are performed by different modules at anygiven time. In one embodiment, the second module 304 includes aplurality of data and optional servo readers 331 and no writers. Thefirst and third modules 302, 306 include a plurality of writers 322 andno data readers, with the exception that the outer modules 302, 306 mayinclude optional servo readers. The servo readers may be used toposition the head during reading and/or writing operations. The servoreader(s) on each module are typically located towards the end of thearray of readers or writers.

By having only readers or side by side writers and servo readers in thegap between the substrate and closure, the gap length can besubstantially reduced. Typical heads have piggybacked readers andwriters, where the writer is formed above each reader. A typical gap is20-35 microns. However, irregularities on the tape may tend to droopinto the gap and create gap erosion. Thus, the smaller the gap is thebetter. The smaller gap enabled herein exhibits fewer wear relatedproblems.

In some embodiments, the second module 304 has a closure, while thefirst and third modules 302, 306 do not have a closure. Where there isno closure, preferably a hard coating is added to the module. Onepreferred coating is diamond-like carbon (DLC).

In the embodiment shown in FIG. 5, the first, second, and third modules302, 304, 306 each have a closure 332, 334, 336, which extends the tapebearing surface of the associated module, thereby effectivelypositioning the read/write elements away from the edge of the tapebearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures334, 336 of the first and third modules 302, 306, however, may beshorter than the closure 332 of the second module 304 as measuredparallel to a direction of tape travel over the respective module. Thisenables positioning the modules closer together. One way to produceshorter closures 334, 336 is to lap the standard ceramic closures of thesecond module 304 an additional amount. Another way is to plate ordeposit thin film closures above the elements during thin filmprocessing. For example, a thin film closure of a hard material such asSendust or nickel-iron alloy (e.g., 45/55) can be formed on the module.

With reduced-thickness ceramic or thin film closures 334, 336 or noclosures on the outer modules 302, 306, the write-to-read gap spacingcan be reduced to less than about 1 mm, e.g., about 0.75 mm, or 50% lessthan commonly-used LTO tape head spacing. The open space between themodules 302, 304, 306 can still be set to approximately 0.5 to 0.6 mm,which in some embodiments is ideal for stabilizing tape motion over thesecond module 304.

Depending on tape tension and stiffness, it may be desirable to anglethe tape bearing surfaces of the outer modules relative to the tapebearing surface of the second module. FIG. 6 illustrates an embodimentwhere the modules 302, 304, 306 are in a tangent or nearly tangent(angled) configuration. Particularly, the tape bearing surfaces of theouter modules 302, 306 are about parallel to the tape at the desiredwrap angle α₂ of the second module 304. In other words, the planes ofthe tape bearing surfaces 308, 312 of the outer modules 302, 306 areoriented at about the desired wrap angle α₂ of the tape 315 relative tothe second module 304. The tape will also pop off of the trailing module306 in this embodiment, thereby reducing wear on the elements in thetrailing module 306. These embodiments are particularly useful forwrite-read-write applications. Additional aspects of these embodimentsare similar to those given above.

Typically, the tape wrap angles may be set about midway between theembodiments shown in FIGS. 5 and 6.

FIG. 7 illustrates an embodiment where the modules 302, 304, 306 are inan overwrap configuration. Particularly, the tape bearing surfaces 308,312 of the outer modules 302, 306 are angled slightly more than the tape315 when set at the desired wrap angle α₂ relative to the second module304. In this embodiment, the tape does not pop off of the trailingmodule, allowing it to be used for writing or reading. Accordingly, theleading and middle modules can both perform reading and/or writingfunctions while the trailing module can read any just-written data.Thus, these embodiments are preferred for write-read-write,read-write-read, and write-write-read applications. In the latterembodiments, closures should be wider than the tape canopies forensuring read capability. The wider closures may require a widergap-to-gap separation. Therefore, a preferred embodiment has awrite-read-write configuration, which may use shortened closures thatthus allow closer gap-to-gap separation.

Additional aspects of the embodiments shown in FIGS. 6 and 7 are similarto those given above.

A 32 channel version of a multi-module head 126 may use cables 350having leads on the same or smaller pitch as current 16 channelpiggyback LTO modules, or alternatively the connections on the modulemay be organ-keyboarded for a 50% reduction in cable span. Over-under,writing pair unshielded cables may be used for the writers, which mayhave integrated servo readers.

The outer wrap angles α₁ may be set in the drive, such as by guides ofany type known in the art, such as adjustable rollers, slides, etc. oralternatively by outriggers, which are integral to the head. Forexample, rollers having an offset axis may be used to set the wrapangles. The offset axis creates an orbital arc of rotation, allowingprecise alignment of the wrap angle α₁.

To assemble any of the embodiments described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may bemaintained or even reduced relative to heads of previous generations. Inother approaches, the modules may be constructed as a unitary body.Those skilled in the art, armed with the present teachings, willappreciate that other known methods of manufacturing such heads may beadapted for use in constructing such heads. Moreover, unless otherwisespecified, processes and materials of types known in the art may beadapted for use in various embodiments in conformance with the teachingsherein, as would become apparent to one skilled in the art upon readingthe present disclosure.

As mentioned above, magnetic tapes often include defects disseminatedacross the surface area of the tape, and which protrude therefrom. Intape recording, the media runs in contact with the head, thus making thetransducers susceptible to effects of media defects. For example,defects can scratch the leading sensor shield or other layer, and smearconductive material across the sensor, thereby creating a short. Suchshort adversely affects the signal derived from the sensor, and in manycases renders the sensor non-functional.

Friction between asperities on the tape and the ductile metallic filmsin the sensor gives rise to deformation forces in the direction of tapemotion. As a result, an electrical short is created by the scratchingand/or smearing across the layers, where the shorting has a net effectof creating bridges of conductive material across the sensor.Particularly, the lapping particles may plow through ductile magneticmaterial, e.g., from one or both shields, smearing the metal across theinsulating material, and thereby creating an electrical short thatreduces the effective resistance of the sensor and diminishes thesensitivity of the sensor as a whole.

Scientists and engineers familiar with tape recording technology wouldnot necessarily expect a CPP MR sensor to remain operable in a contactrecording environment, such as tape data storage, because of a highprobability that abrasive asperities embedded in the recording mediumwill scrape conductive material across the thin insulating layer duringtape travel, thereby creating the aforementioned shorting.

Typical CPP MR sensors such as TMR sensors in hard disk driveapplications are configured to be in electrical contact with the top andbottom shields of read head structures. In such configurations thecurrent flow is constrained to traveling between the top shield and thebottom shield through the sensor, by an insulator layer with a thicknessof about 3 to about 10 nanometers (nm). This insulator layer extendsbelow the hard bias magnet layer (if present) to insulate the bottom ofthe hard bias magnet from the bottom shield/lead layers, and isolatesthe edges of the sensor from the hard bias magnet material. In a tapeenvironment, where the sensor is in contact with the tape media, in onemode, smearing of the top or bottom shield material can bridge theinsulation layer separating the hard bias magnet from the bottom leadand lower shield, thereby shorting the sensor. Further, in another mode,shield deformation or smearing or sensor layer smearing can create aconductive bridge across a tunnel barrier layer in a TMR sensor. Suchtunnel barrier layer may be only 12-15 angstroms thick or less.

In disk drives, conventional CPP MR designs are acceptable because thereis minimal contact between the head and the media. However, for taperecording, the head and the media are in constant contact. Head coatinghas been cited as a possible solution to these shorting issues; however,tape particles and asperities have been known to scratch through and/orwear away these coating materials as well. Because the insulating layersof a conventional CPP MR sensor are so thin, the propensity forelectrical shorting due, e.g., to scratches, material deposits, surfacedefects, films deformation, etc., is relatively high.

Burnishing may be employed in an attempt to effectively “blunt” suchdefects and mitigate their effect on transducers. However, productionlimitations associated with cost limit the time available forburnishing. Even when burnishing is performed on a given tape, existingsystems are unable to determine if the burnishing performed was adequatein the limited time available.

In sharp contrast, various embodiments described herein are able todetect defects and/or determine if the amount of burnishing performed ona given media meets specified requirements. Thus, embodiments describedherein may be able to determine whether the amount of burnishingperformed is sufficient to reduce the likelihood of damaging transducersbrought into contact therewith to an acceptable level. Moreover, mediathat does not meet requirements (e.g., that has not been sufficientlyburnished) may be dealt with accordingly, e.g., by being burnishedfurther, rejected entirely, reformulated to fix the particular issue,etc., as will be described in further detail below.

FIGS. 8A-8B depict an apparatus 800 in accordance with one embodiment.As an option, the present apparatus 800 may be implemented inconjunction with features from any other embodiment listed herein, suchas those described with reference to the other FIGS. However, suchapparatus 800 and others presented herein may be used in variousapplications and/or in permutations which may or may not be specificallydescribed in the illustrative embodiments listed herein. Further, theapparatus 800 presented herein may be used in any desired environment.

Apparatus 800 includes a plurality of detector structures 802 positionedin a first array 804 and one or more write transducers 806 positioned ina second array 808. Moreover, a servo reader 816 may be positioned oneither side of the array 808 of write transducers 806, e.g., to enabletrack following during detection as described below. The servo readers816 are positioned to read servo tracks 822 on the magnetic tape. In thepresent illustrative embodiment, five servo tracks 822 are shown,defining four servo bands therebetween.

The detector structures 802 are preferably configured such that they maybe used to detect defects on a magnetic medium, e.g., such as asperitiesprotruding from the surface of a magnetic tape. As alluded to above, theability to detect such defects on a magnetic medium may reduce thelikelihood of damaging transducers brought into contact with themagnetic medium during use. For example, the quantity and/or severity ofdefects detected on a given magnetic medium may be compared with qualitycontrol levels for that magnetic medium to determine whether the mediumis fit for use. Depending on whether a magnetic medium meetscorresponding quality control levels, action may be taken as desired(e.g., see method 1000 below). It should be noted that variousapproaches included below are described with reference to magnetic tape;however, this is in no way intended to limit the invention, but ratheris presented by way of example only. Any of the approaches describedherein may be implemented with any other desired type of magneticmedium.

Referring specifically now to the detailed view in FIG. 8B, each of thedetector structures 802 preferably include a pair of conductive layers812 separated by an insulating material 814. According to the presentembodiment, the insulating material 814 is the only layer positionedbetween the conductive layers 812 in each of the detector structures802. Thus, a distance D separating the conductive layers of each of thedetector structures 802, measured in an intended direction of magneticmedia travel 811, may be reduced, e.g., compared to a shield-to-shieldspacing in a standard read sensor. The distance D may be in a range offrom about 2 nm to about 10 nm, but could be higher or lower, e.g.,depending on the desired approach. Thus, a thickness T₁ of theinsulating material 814 measured in the intended direction of magneticmedia travel 811 may be in a range of from about 2 nm to about 10 nm,but could be higher or lower, e.g., depending on the desired approach.Furthermore, a thickness T₂ of one or both of the conductive layers 812may be in a range of from about 50 nm to about 1.2 μm, but could behigher or lower. Because the thickness T₁ is so small, the detectorstructure is prone to shunting due to pinholes and possible damage dueto electrostatic discharge (ESD). Accordingly, the stripe height of theconductive layers 812, measured in a direction into the page of FIGS. 8Aand 8B, is preferably small to minimize the surface area of the opposingfaces of the conductive layers 812, thereby reducing the probability ofsuch shunts occurring, e.g., via pinholes. Therefore, electronic lappingguides (ELGs) 818 of conventional construction may be used to control anextent of lapping in the stripe height direction when setting the stripeheight of the conductive layers. Preferably, an ELG is provided for eachdetector structure, but more of fewer ELGs may be present. Anillustrative stripe height of the conductive layers 812 may be in arange of about 0.2 to about 0.8 microns, but could be higher or lower.

A resistor 819 may be connected between the conductive layers 812 toprevent charge buildup on one of the conductive layers 812, therebyreducing the chance of an ESD event. The resistor may be of conventionalconstruction, and may be internal or external. In one approach, an ELGmay serve as the resistor.

In some approaches, the insulating material 814 may be recessed relativeto the conductive layers 812 (not shown) in a direction perpendicular tothe plane created by the intended direction of magnetic media travel 811and the cross-track direction 810. Recessing the insulating material 814relative to the conductive layers 812 may increase the likelihood that adefect will create a smear from one conductive layer to the other, andtherefore recession may be included to increase sensitivity of thedetector structures 802. According to an exemplary approach, theinsulating material 814 may be recessed 2 nm or more relative to theconductive layers 812, but the recession could be higher or lower.

It follows that any one or more of the detector structures 802 may notinclude an operable reader for reading data from a magnetic tape.Consequently, the detector structures 802 are not physically capable ofreading written data in the present embodiment. However, the detectorstructures 802 are able to allow detection of defects on a magnetic tapepassed thereover.

In other embodiments, the detector structures 802 may include CPPsensors such as tunnel valve sensors. The widths of such detectorstructures 802 with sensors may be wider than would be practical fordata reading operations, so as to cover more surface area of the tapepassing thereby to maximize detection. The distance D between theconductive layers 812 may be larger than previously described toaccommodate the sensor stack. In some embodiments, such CPP sensors maynot have hard bias magnets, which could otherwise result in a larger D.

As a magnetic medium (e.g., tape) is passed over the detector structures802, defects on the magnetic medium may cause material from one of theconductive layers 812 to smear across the insulating material 814, andto the opposite conductive layer 812. As would be appreciated by oneskilled in the art upon reading the present description, creating such asmear of conducive material across the insulating material 814 may causeat least a partial electrical short (e.g., a detectable drop in theresistance value between the conductive layers 812). Thus, by measuringand monitoring a resistance value between the conductive layers 812,defects on a magnetic tape may be identified by noting changes in theresistance value for a given detector structure 802. It should bementioned that while some shorts may render the detector structures 802inoperative, other shorts may not render the detector structures 802inoperative, i.e., the detector structure can continue to be used.

FIG. 8B depicts a representation of an illustrative detector circuit 830that may be used to detect the change in resistance value for thedetector structure 802 coupled thereto. The illustrative detectorcircuit 830 shown includes an ohmmeter 832, but other embodiments mayuse any other mechanism that would become apparent to one skilled in theart upon reading the present disclosure.

Moreover, when a defect is identified by noting a change in theresistance value for a given detector structure 802, the writetransducers 806 may be used to write a signal burst at about thelocation of the defect for later identification (e.g., again see method1000 below). The signal burst is preferably a short and an easilyrecognized pattern, e.g., such as a 12 T pattern, as would beappreciated by one skilled in the art upon reading the presentdescription. The signal burst may include encoded (written) data in someapproaches, but other approaches the signal burst may simply be amagnetic transition, sequence of transitions, pattern, etc. that iseasily detectable.

It should also be noted that in some embodiments, a resistor (not shown)may be coupled between the conductive layers 812 in each of the detectorstructures 802. Doing so may help prevent electrostatic discharge (ESD)from affecting the apparatus 800. The resistor would preferably have ahigh resistance value, e.g., about 1,000Ω or more, but could be higheror lower, as would be appreciated by one skilled in the art upon readingthe present description. Thus, when material is smeared from one of theconductive layers 812 to the opposite conductive layer 812 across theinsulating material 814, a detectable drop in resistance between theconducive layers may be noted rather than a jump from an effectivelyopen circuit to an effectively shorted circuit. It should also be notedthat a detector structure 802 may continue to function (be used todetect defects) despite experiencing a smear between the conductivelayers 812. A detector structure retains at least some sensitivity evenafter a smearing between the conductive layers 812 has occurred. Thus,after a defect has been detected, a sensitivity associated with thedetector structure 802 that detected the defect may be accounted for tocompensate for the reduction in responsiveness thereof so that thedetector structure 802 may continue to be used.

In some approaches, the conductive layers 812 of apparatus 800 mayinclude permalloy, e.g., such that the conductive layers 812 resemblemagnetic shields typically included in transducers of magnetic tapeheads. Thus, the conductive layers 812 may be able to accuratelyrepresent the manner in which the transducers of an actual magnetic headwould be effected by the magnetic tape. It follows that any of thecomponents, dimensions, materials, etc. as described herein may betailored to resemble those used in actual magnetic heads (e.g., in atape library, tape drive, etc.) in order to identify defects that wouldhave a negative effect on such actual magnetic heads. None of thespecific embodiments included herein are intended to be limiting, butrather are presented by way of example.

For instance, in other approaches the conductive layers 812 may includeany desired electrically conductive material to enable monitoring aresistance value of each of the detector structures. The conductivelayers 812 may be of the same material, or may be different materials.Laminated conductive layers 812 may be used in some embodiments.

Performing experiments with conductive layers 812 of particularmaterials may enable ranking of the susceptibility to smearing ofparticular materials.

Where the conductive layers 812 are of differing materials, the effectof tape defects may be studied by running the tape in both directions,and determining in which direction a smear occurs. If smearing occurs ina particular direction and not the other, then the material of theleading conductive layer at the time of smearing can be investigated asa potentially smearable material.

In a further approach, the conductive layers in each pair may be ofdifferent composition, and the compositions of some of the conductivelayers in one or both rows are different than other of the conductivelayers in the same row. Any arrangement is possible. For example, thematerials may alternate across the array, e.g., the leading array may beconfigured as follows: Sendust, permalloy, Sendust, permalloy . . . ;while the trailing array is configured as follows: permalloy, Sendust,permalloy, Sendust . . . . This configuration enables comparison ofdifferent materials, as well as media defects that are asymmetrical andthus create more pronounced smearing in one direction vs. the other. Insuch embodiments, the tape would ideally be run in both directions. Suchembodiments may be configured as in FIGS. 9A and/or 9B, for example.

The insulating material 814 may include alumina according to anexemplary approach, but may include any known electrically insulatingmaterial to prevent current to pass between the conductive layers 812.The insulating material 814 may include a laminated structure ofdiffering materials. Similarly, the array 804 of detector structures 802may include a coating formed over a media facing surface thereof. Insome approaches, the coating may resemble a magnetic head coating usedon the media facing surface of magnetic heads, e.g., such as alumina,diamond-like-carbon, etc. to more accurately simulate productconditions. However, in other approaches the array 804 of detectorstructures 802 may not include a coating to alter the sensitivity of thedetector structures 802.

Looking again to FIG. 8A, the array 804 of detector structures 802 areshown as spanning wider in the cross-track direction 810 than the array808 of write transducers 806, as measured from outermost writetransducers 806, or between the servo readers 816. The wider thedetector structures 802 span in the cross-track direction 810, the moreof the tape the detector structures 802 are able to monitor for defects.Thus, it is preferred that the plurality of detector structures 802 spanat least as wide in the cross-track direction 810 as the array 808 ofwrite transducers 806 do. In some embodiments, the detector structures802 span wider in the cross-track direction 810 than the writetransducers 806 do. In an exemplary approach, the array 808 of writetransducers 806 may span wide enough in the cross-track direction 810such that a width thereof corresponds to the width of a single data bandof a magnetic tape being passed over the write transducers 806.

According to various other approaches, the width W of the array 804 ofthe plurality of detector structures 802 may span across less than atotal width (in the cross-track direction 810) of a magnetic tape beingpassed over the detector structures 802, e.g., at least 25%, at least30%, at least 45%, at least 50%, at least 60%, at least 75%, at least80%, at least 90%, at least 95%, etc. of the total width of a magnetictape being passed over the detector structures 802, but could be higheror lower.

FIG. 8C depicts an embodiment 840 in which the width W of the array 804of the detector structures 802 is about equal to the width of one databand, as defined between adjacent servo tracks 822. Accordingly, thetape may be passed over the array 804 of the detector structures 802four times, with the array being stepped sequentially into the next databand after each pass. Moreover, if a tape is known to have a defect,e.g., the tape caused a short during a read/write operation and thus thedata band in use at the time is known, the present embodiment may beused to detect that defect.

FIG. 8D depicts an embodiment 850 in which the width W of the array 804of the detector structures 802 is about equal to the width of two databands. Accordingly, the tape may be passed over the array 804 of thedetector structures 802 two times, with the array being stepped to theother half of the tape after a first pass.

The spacing between adjacent detector structures 802 is preferably smallto minimize the amount of tape that passes between the detectorstructures 802. Preferably, the sum of the widths of the detectorstructures 802 is at least 90% of the width W of the array, ideally atleast 95% of the width W of the array.

Moreover, the width of each of the detector structures 802 measured inthe cross-track direction 810 may vary depending on the number ofdetector structures included in the array, the overall width of thearray of detector structures, a spacing between each of the detectorstructures in the cross-track direction, etc. According to an example,which is in no way intended to limit the invention, the array 804 ofdetector structures 802 may include 12 detector structures spanningacross the total width of a magnetic tape being passed thereover, eachof the detector structures 802 having a width of about 1 mm measured inthe cross-track direction 810, and a space X of about 2 μm between eachpair thereof. In another exemplary embodiment, a 24 detector structures802, each having a width of about 0.5 mm measured in the cross-trackdirection 810 may be included. However, in other approaches an apparatusmay include 1 detector structure that spans the entire desired width, atleast 2 detector structures, 10 detector structures, at least 16detector structures, 35 detector structures, etc. A benefit of havingmore detector structures is that the portion of the tape having thedefect is more precisely determined, e.g., by correlating the section oftape with the position of the particular detector structure 802 thatexperienced the short.

It should also be noted that although a plurality of write transducers806 are included in the present embodiment, in other embodiments fewerwrite transducers may be included. As mentioned above, in someapproaches, only a single write transducer may be included. The singlewrite transducer may span wider in the cross-track direction 810 incomparison to a standard write transducer, or may have dimensionssimilar to any conventional write transducer, e.g., depending on thedesired approach. It is preferred that at least one write transducer isincluded, however some embodiments may not have any write transducers,as will be described in further description below.

In further embodiments, write transducers may be aligned with thedetector structures in the tape travel direction. This may improvedetection, as the written signal burst may be written by the writer inalignment with the position of the detector structure that encounteredthe defect. For example, FIG. 8E depicts an embodiment having a writetransducer 808 aligned with each detector structure 802. The writetransducers 808 are positioned on a second module 809. However, as shownin FIG. 8F, the write transducers 808 may be positioned on the samemodule 805 as the detector structures 802. In some approaches, the writetransducers 808 may be centered with respect to the detector structure802 associated therewith. In other approaches, the write transducers 808may be offset laterally with respect to the detector structure 802associated therewith.

The write transducers in various embodiments may be configured to writepredefined patterns, e.g., in response to a detector structureencountering a defect. The patterns may be configured to provide anydesired information. For example, where each write transducer writes asignal burst in a unique pattern that is specific to that writetransducer and different than patterns the other write transducerswrite, the pattern can later be used to identify which writer wrote thewritten signal burst. In other approaches, more than one writer maywrite a signal burst, where the relative positions and/or writtentransitions of the signal bursts has some predefined significance.

Referring again to the embodiment illustrated in FIGS. 8A-8B, the firstand second arrays 804, 808 are oriented in a cross-track direction 810,but in other approaches the first and/or second array 804, 808 may haveany desired orientation. For example, the first and/or second array 804,808 may be oriented at an angle relative to the cross-track direction810, oriented along a curved line, interleaved among other components,etc. depending on the desired approach.

The first and second arrays 804, 808 are also positioned on first andsecond modules 805, 809, respectively, which may be positioned relativeto each other to wrap a tape such as the head in FIG. 2. However, inother approaches, the first and/or second array 804, 808 may bepositioned on a common (single) module, a third module may beimplemented (e.g., see FIGS. 9A-9B), a fourth module may be included,etc. Again, the specific implementations illustrated in apparatus 800 ofFIGS. 8A-8B are in no way intended to limit the invention.

Referring momentarily to FIGS. 9A-9B, apparatuses 900, 950 are shown inaccordance with one embodiment. As an option, the present apparatuses900, 950 may be implemented in conjunction with features from any otherembodiment listed herein, such as those described with reference to theother FIGS., such as FIGS. 8A-8B. Specifically, FIGS. 9A-9B illustratevariations of the embodiment of FIGS. 8A-8B depicting several exemplaryconfigurations within the apparatuses 900, 950. Accordingly, variouscomponents of FIGS. 9A-9B have common numbering with those of FIGS.8A-8B.

However, such apparatuses 900, 950 and others presented herein may beused in various applications and/or in permutations which may or may notbe specifically described in the illustrative embodiments listed herein.Further, the apparatuses 900, 950 presented herein may be used in anydesired environment. Thus FIGS. 9A-9B (and the other FIGS.) may bedeemed to include any possible permutation.

As shown in FIG. 9A, apparatus 900 includes first and second arrays 804,808 of detector structures 802 and write transducers 806, respectively,positioned on first and second modules 805, 809, respectively. However,in addition to the first and second arrays 804, 808, apparatus 900includes a third array 904 of detector structures 902 positioned on athird module 906. Detector structures 902 preferably have the same orsimilar composition as detector structures 802, but they may bedifferent (e.g., have different widths, different material compositions,a different number of detector structures in the array 904, etc.)depending on the desired approach. Moreover, according to differentapproaches, any one or more of the modules may have beveled edges,rather than skiving edges. In one approach, the second module 809 (thecenter module) may have beveled edges. Depending on how the modules arearranged to wrap the tape, the downstream module may or may not engagethe tape.

By including a third array 904 of detector structures 902 positioned onan opposite side of the second array 808 of write transducers 806 as thefirst array 804 of detector structures 802, apparatus 900 enablesbi-directional functionality. As mentioned above, the write transducers806 may be used to write a signal burst at about the longitudinallocation of an identified defect on a magnetic tape being examined, andtherefore it is preferred that the write transducers 806 are positionedin the down-track direction relative to the detector structures 902being used. Once a defect is detected by one or more of the detectorstructures 902, one or more write transducers 806 may be directed towrite the signal burst when the longitudinal position generallycorresponding to the defect(s) passes over a down-stream writetransducer 806 such as by delaying writing of the signal burst by thetime of transit between the detector and the trailing writer as afunction of distance between the detector and the trailing writer andtape velocity (e.g., again see method 1000 below). It follows that thesecond array 808 of write transducers 806 and the leading array ofdetector structures are active depending on the particular intendeddirection of tape travel. Thus, apparatus 900 may be configured suchthat the magnetic tape may fly over the downstream array of detectorstructures according to any of the approaches described herein, e.g., asthe downstream array may not be active (e.g., used). By including athird array 904 of detector structures 902 positioned on an oppositeside of the second array 808 of write transducers 806 as the first array804 of detector structures 802, defects may be detected and flagged onthe magnetic tape regardless of the direction the magnetic tape istraveling. Moreover, a tape may be run in both directions to help ensurethere are no defects that are more destructive in one direction of tapetravel than the other.

FIG. 9B illustrates an alternate embodiment which also allows forbi-directional functionality. However, rather than having arrays ofdetector structures positioned on either side of the write transducersalong the intended direction of magnetic media travel 811, apparatus 950includes first and second arrays 804, 808 of detector structures 802 andwrite transducers 806, respectively, as well as a third array 954 ofwrite transducers 952 and servo readers 956 positioned on an oppositeside of the first array 804 of detector structures 802 as the secondarray 808 of write transducers 806. Moreover, the first, second andthird arrays 804, 808, 954 are shown as included on a single module 958.However, as previously mentioned, the arrays of a given embodiment maybe included on any number of desired modules.

Similar to the approach described above, here the first array 804 ofdetector structures 802 and the downstream array of write transducersmay be active depending on the particular direction of tape travelthereacross. Thus, it is preferred that the magnetic tape does not flyover the downstream array. Again, by implementing a third array 954,apparatus 950 enables bi-directional functionality depending on thedirection the magnetic tape is traveling as described above.

Referring again to FIGS. 8A-8B, the modules 805, 809 may be included ina magnetic head, e.g., see 126 of FIG. 1A, thereby enabling magnetictape to be passed over the components included in the first and secondarrays 804, 808 on the modules 805, 809. Moreover, although theinsulating material 814 is the only layer positioned between theconductive layers 812 in each of the detector structures 802 such thatnone of the detector structures 802 include an operable reader forreading data from a magnetic tape, in some embodiments a detectorstructure may include a read transducer. Accordingly, in someembodiments read transducers may be repurposed to serve as detectorstructures for detecting defects on a magnetic tape. In some approaches,the modules 805, 809 and arrays 804, 808 described herein may beimplemented in a tape drive, or another configuration that allows fortape to be passed thereover.

As mentioned above, once a defect is detected on a magnetic tape by oneor more detector structures, one or more write transducers may bedirected to write a signal burst to the magnetic tape when the lateralposition corresponding to the defect(s) passes over a down-stream writetransducer. FIG. 10 illustrates a flowchart of a computer-implementedmethod 1000 for conducting such a process according to one embodiment.The method 1000 may be performed in accordance with the presentinvention in any of the environments depicted in FIGS. 1-9B, amongothers, in various embodiments. Of course, more or less operations thanthose specifically described in FIG. 10 may be included in method 1000,as would be understood by one of skill in the art upon reading thepresent descriptions.

Each of the steps of the method 1000 may be performed by any suitablecomponent of the operating environment. For example, in variousembodiments, the method 1000 may be partially or entirely performed by acontroller, a processor, etc., or some other device having one or moreprocessors therein. The processor, e.g., processing circuit(s), chip(s),and/or module(s) implemented in hardware and/or software, and preferablyhaving at least one hardware component may be utilized in any device toperform one or more steps of the method 1000. Illustrative processorsinclude, but are not limited to, a central processing unit (CPU), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), etc., combinations thereof, or any other suitablecomputing device known in the art. In one approach, the method isperformed by the controller of a tape drive.

As shown in FIG. 10, method 1000 includes monitoring a resistance valueof each of a plurality of detector structures individually. Seeoperation 1002. The detector structures may be positioned in an arrayaccording to any of the approaches illustrated in FIGS. 8A-9B. Thus theplurality of detector structures that the resistance value is monitoredacross may depend on such factors as the intended direction of mediatravel (e.g., tape travel), the orientation of detector structures withrespect to write transducers, whether write transducers are included ina given embodiment (e.g., see FIG. 11), etc.

According to one approach, operation 1002 may include monitoring aresistance value of each of the plurality of detector structures of twodifferent arrays, (e.g., such as arrays 804 and 904 of FIG. 9A), forredundancy. Thus, if a defect is detected by a detector structure in aleading one of the arrays 804, 904, the trailing one of the arrays 804,904 may be used to verify the defect, e.g., by determining whether adetector structure in the trailing array which corresponds to (alignswith) the detector structure in the leading array also detects thedefect.

With continued reference to method 1000, decision 1004 determineswhether the resistance value of any of the plurality of detectorstructures being monitored drops below a predetermined threshold. Asdescribed above, each of the detector structures preferably include apair of conductive layers (e.g., shields) which are separated by anelectrically insulating material. Either conductive layer and/or theelectrically insulating material may include any of the types ofmaterials described herein, e.g., depending on the desired approach.Momentarily referring back to FIGS. 8A-8B, as a magnetic medium (e.g.,tape) is passed over detector structures 802, defects on the magneticmedium may cause material from one of the conductive layers 812 to smearacross the insulating material 814, to the opposite conductive layer812. The smear of conducive material across the insulating material 814may cause at least a partial electrical short in the detector structure802. Thus, by measuring and monitoring a resistance value between theconductive layers 812 of the detector structure 802, defects on amagnetic tape may be identified by noting changes in the resistancevalue.

While a change in resistance value is used in this exemplary embodiment,any known method enabling detection of a short may be used in variousembodiments. For example, equivalently to detecting whether resistancevalues fall below a threshold, mere detection of a current may indicatepresence of a short. Similarly, detection of a change in voltage may beindicative of a short.

It should also be noted that in some embodiments, none of the detectorstructures include an operable reader for reading data from a magnetictape. However, this is in no way intended to limit the invention. Forinstance, in other embodiments, one or more of the plurality of detectorstructures may simply be a read transducer, and may thereby include anoperable reader, e.g., for reading data from a magnetic tape and/orservo readers for positioning the tape.

Referring again to method 1000 of FIG. 10, it should be noted that“below a threshold” is in no way intended to limit the invention. Ratherthan determining whether a value is below a threshold, equivalentdeterminations may be made, e.g., as to whether a value is within apredetermined range, whether a value is outside a predetermined range,whether an absolute value is above a threshold, whether a value is abovea threshold, etc., depending on the desired approach.

As shown, method 1000 returns to operation 1002 in response todetermining that the resistance value of all of the plurality ofdetector structures has not dropped below a predetermined threshold.Upon returning to operation 1002, the resistance value of each of aplurality of detector structures individually may continue to bemonitored. However, method 1000 proceeds to operation 1006 in responseto determining that the resistance value of any of the plurality ofdetector structures drops below a predetermined threshold. In otherwords, method 1000 proceeds to operation 1006 in response to detecting asufficient change in a resistance value of at least one of the detectorstructures, which includes identifying a defect on a magnetic tape beingrun over the detector structures.

However, the defect may have caused a smear to occur anywhere along thewidth of the detector structure. Thus, operation 1006 may be limited inthe amount of detail with which the location of the defect along thewidth of the magnetic tape may be identified, e.g., depending on thewidth of the detector structure, the number of detector structures, etc.Thus, fewer wider, or additional narrower, detector structures may beincluded in a given embodiment, e.g., depending on the desired precisionby which the embodiment may be able to detect defects along thecross-track direction.

Moreover, operation 1008 includes using a servo reader to determine aposition along a length of the magnetic tape that corresponds to anidentified defect. An embodiment may include one or more servo readersin order to determine a position along the length of a magnetic tapethat corresponds to a detected defect thereon, in addition to otherfunctions such as track following and skew following. According to oneapproach, the servo reader may determine the position along the lengthof the magnetic tape corresponding to an identified defect by usinglinear position (LPOS) information encoded in a servo track. The servoreader may be instructed to identify an LPOS from the servo track when adefect is identified, preferably simultaneously. Thus, the LPOS of thedefect along the length of the magnetic tape may be determined andstored for later use to locate the defect. The positions along a lengthof the magnetic tape which correspond to identified defects may bestored in memory, sent to a user, compiled in a table, used to determinewhether the magnetic media meets specified requirements, etc.

In another embodiment, the servo reader may be used to help keep thearray of detector structures at a fixed lateral position relative to themagnetic tape. By keeping the array of detector structures at a fixedlateral position relative to the magnetic tape, one or more defects maybe passed over the same location on the detector structures, e.g., toensure that they are detected. Thus, in some approaches, the arrays ofdetector structures and write transducers may be included in atrack-following actuator assembly as would be appreciated by one skilledin the art upon reading the present description.

Preferably, tape skew following is also applied for even greaterpositioning accuracy. If tape skew is not corrected for, and multiplepasses of the tape over the head are performed, there is a possibilitythat the resulting smears will likely not be formed in the samelocation. Servo readers on different modules may be used to detect tapeskew.

Method 1000 further includes using at least one write transducer towrite a signal burst on a magnetic tape at about a position of theidentified defect along a length of the magnetic tape. See operation1010. Again, write transducers may be used to write a signal burst nearthe location of an identified defect on a magnetic tape being examined,and therefore it is preferred that the write transducers are positionedin the down-track direction relative to detector structures being usedas described herein. Once a defect is detected by one or more of thedetector structures, one or more (e.g., all) write transducers may betriggered to write the signal burst when the lateral positioncorresponding to the defect(s) passes over the down-stream writetransducers. The signal burst is preferably short and an easilyrecognized pattern, e.g., such as a 12 T pattern, as would beappreciated by one skilled in the art upon reading the presentdescription. The signal burst may include encoded (written) data in someapproaches, but other approaches the signal burst may simply be apattern that is easily detectable.

For situations where the trigger is produced as a result of an upstreammodule detecting a defect on a magnetic tape, a delay in writing thesignal burst is preferably implemented such that the signal burst iswritten at about the same longitudinal location as the detected defect.In other words, a time delay corresponding to the amount of time ittakes for the magnetic tape to travel from the detector structures tothe downstream writer transducers is preferably implemented beforewriting the signal burst. Accordingly, the leading edge of the signalburst may align with the location of the defect. Moreover, the delay mayvary depending on the speed at which the magnetic tape is traveling, thesize of the defect, the spacing between the detector structures and thewrite transducers, etc. This further improves the ability to laterlocate the location of the defect on the magnetic tape. With standardpositioning accuracy, a defect may be located in an area approximately 1mm² or smaller, e.g., depending on the number of detectors.

Moreover, because the array of detector structures preferably spans atleast as wide in the cross-track direction as the write transducers(e.g., see FIGS. 8A-9B), and ideally greater, it is possible that thedefect is detected by a detector structure at a position along thecross-track direction that does not align with any of the writetransducers in the intended direction of media travel. Thus, the signalburst may not correspond to the actual location of the identifieddefect. Rather, the signal burst may simply indicate a position alongthe length of the tape where the defect is located. The defect maytherefore be located somewhere along the cross-track direction fromwhere the signal burst was written to the magnetic tape. In someapproaches, the LPOS information collected by one or more servo readersmay be utilized in combination with the signal bursts written to themagnetic tape to later locate the defects. According to an example,which is in no way intended to limit the invention, a user may utilizethe LPOS information corresponding to a detected defect to determine ageneral location of a defect on a magnetic tape. After accessing aportion of the tape corresponding to the LPOS information, a user mayinspect the tape for the signal burst written thereto. Moreover, afterlocating the signal burst on the tape, a user may visually inspect thetape along a width thereof that passes through the signal burst. Thisprocess may be repeated for any one or more of the other identifieddefects for the magnetic tape.

Inspecting the tape for the signal burst written thereto and/or for thedefect itself may include using conventional readers to detect thesignal burst to identify the approximate location of the defect, andthen inspecting the surface of the tape using a technique such asatomic-force microscopy (AFM), etc., or any other form of inspecting thetape which would be apparent to one skilled in the art upon reading thepresent description. See also the method of FIG. 12, described below.

Referring still to FIG. 10, method 1000 additionally includes evaluatinga number of identified defects per unit surface area of a magnetic tapeto determine a quality of the magnetic tape. See operation 1012.According to some approaches, a whole magnetic tape may be examined fordefects thereon before the results are evaluated according to operation1012. However, in other approaches, the number of defects identified ona magnetic tape may be evaluated according to operation 1012 after asufficient amount (e.g., length) of the magnetic tape has been examined,e.g., such as at least a quarter of the total length of the magnetictape, at least half of the total length of the magnetic tape, at least aunit service area of the magnetic tape, etc. Accordingly, the evaluationperformed in operation 1012 may effectively serve as an approximation ofthe defect distribution for the remainder of the magnetic tape.

Furthermore, decision 1014 includes determining whether the quality ofthe magnetic tape falls below a specified requirement. As mentionedabove, different magnetic media may have specified requirements, e.g.,depending on the type of magnetic media, user preferences, sensitivityof data, etc. Thus, by comparing the actual quality of the magnetic tape(e.g., based on the number of identified defects per unit surface areaof a magnetic tape) with a specified requirement, method 1000 maydetermine if the magnetic tape is suitable for use. This may beparticularly beneficial when testing magnetic tape before they areimplemented in an actual tape head in order prevent damage to sensors insuch magnetic heads caused by an undesirably high concentration ofdefects on the magnetic tape. As mentioned above, various embodimentsdescribed herein may be able to detect defects and/or determine if theamount of burnishing performed on a given media meets specifiedrequirements. Thus, embodiments described herein may be able todetermine whether the amount of burnishing performed on a magnetic tapeis sufficient to reduce the likelihood of damaging transducers broughtinto contact therewith to an acceptable level.

Moreover, media that does not meet requirements (e.g., that has not beensufficiently burnished) may be dealt with as desired. Accordingly,operation 1016 includes taking additional action in response todetermining that the quality of the magnetic tape does fall below aspecified requirement. According to various approaches, the additionalaction may include inspecting the defects, burnishing or re-burnishingthe magnetic tape, rejecting the magnetic tape from being used entirely,reformulating the magnetic tape to fix one or more of the particulardefects, etc. As shown, method 1000 returns to operation 1002 inresponse to determining that the quality of the magnetic tape has notfallen below a specified requirement, or once operation 1016 has beenperformed, again such that the resistance value of each of a pluralityof detector structures individually may continue to be monitored.

FIGS. 11A-11B illustrate a representative schematic view of an apparatus1100 having a wiring configuration that may be used to couple thedetector structures to a controller and/or other monitoring device, inaccordance with one embodiment. As an option, the present apparatus 1100may be implemented in conjunction with features from any otherembodiment listed herein, such as those described with reference to theother FIGS., such as FIGS. 8A-10. Specifically, FIGS. 11A-11Billustrates variations of the embodiment of FIGS. 8A-8B depictingseveral exemplary configurations within the apparatus 1100. Accordingly,various components of FIGS. 11A-11B have common numbering with those ofFIGS. 8A-8B.

However, such apparatus 1100 and others presented herein may be used invarious applications and/or in permutations which may or may not bespecifically described in the illustrative embodiments listed herein.Further, the apparatus 1100 presented herein may be used in any desiredenvironment. Thus FIGS. 11A-11B (and the other FIGS.) may be deemed toinclude any possible permutation.

As shown in the representation in FIG. 11B, the detector structures 802of apparatus 1100 may be electrically coupled to input/output (I/O)connection pads 1102 on the detector module 805 using conductive vias1106 of conventional construction. In some approaches, the I/Oconnection pads 1102 may be wire bond pads. Moreover, a device fordetecting a short may be coupled to each pair of the connection pads1102. Illustrative devices include ohmmeters, ammeters, voltagedetectors, etc. In one approach, an ohmmeter 1104 may be coupled to eachpair of the connection pads 1102 such that a resistance between theconductive layers 812 in each of the detector structures 802 may bemonitored for a sufficient change indicating that a defect has come intocontact with the detector structure. The ohmmeters 1104 may in turn becoupled to a controller configured to perform any one or more of theprocesses described herein.

FIGS. 11C and 11D illustrate additional layouts. These embodimentsillustrate that the connection pads 1102 may be generally aligned withthe detector structures 802.

According to another embodiment, an apparatus for detecting defects on amagnetic medium as described herein may include read transducers ratherthan write transducers. For example, the write transducers 806positioned on the second module 809 of FIG. 9A may alternatively be readtransducers which may operate in a normal read mode, e.g., if data hasalready been written to the magnetic medium. Thus, when a defect isidentified by the detector structures, the read transducers may takenote of the data written at about the same position of the defect alongthe magnetic medium and send, store, etc. that data for future use inrelocating the identified defect. The pre-written pattern on the tape ispreferably sequential in nature, e.g., an ascending bit sequence, whichmay repeat if necessary due to the length of the tape, to enable an easyreturn to the proper location, and fine enough to approximate the linearlocation of the defect to within a few nanometers. It follows that writetransducers are preferably used when data has not yet been written tothe magnetic medium being examined for defects, e.g., such as whenexamining an unused tape.

According to yet another embodiment, an apparatus for detecting defectson a magnetic medium as described herein may only include servo readersin addition to the detector structures. The servo readers may functionas described above and take note of a LPOS that corresponds to theposition of an identified defect along the magnetic medium and send,store, etc. that LPOS data for future use in relocating the identifieddefect. However, servo readers are again by no means required for any ofthe embodiments described herein to function successfully.

After one or more of the detector structures in an array have lost asufficient amount of sensitivity from a given number of smearing eventsbetween the pairs of conductive layers thereof, the detector structuresmay preferably be replaced. According to some approaches, individualdetector structures may be replaced with new detector structures. Inother approaches, a module on which the array of detector structures arepositioned may be replaced with a new module having a new array ofdetector structures. In yet another embodiment, a magnetic head havingboth detector structures and write transducers and/or read transducersas described herein may be replaced with a new magnetic head. In afurther embodiment, the tape bearing surface may be gently polished,e.g., in the cross track direction, to remove the short, therebyrehabilitating the head.

As alluded to above, e.g., with reference to operation 1016 of FIG. 10,once the approximate location of the defect has been marked on the tapeaccording to any of the approaches above, the defect may be searched forand found on the tape. According to some embodiments, the procedure forfinding the defect may generally include finding the written signalburst on the tape, and searching the region of the tape in the vicinityof the signal burst for the defect.

FIG. 12 illustrates a flowchart of a method 1200 for finding a defect ona tape according to one embodiment. The method 1200 may be performed inaccordance with the present invention in any of the environmentsdepicted in FIGS. 1-11B, among others, in various embodiments. Ofcourse, more or less operations than those specifically described inFIG. 12 may be included in method 1200, as would be understood by one ofskill in the art upon reading the present descriptions.

Each of the steps of the method 1200 may be performed by any suitablecomponent of the operating environment and/or by or under the directionof a human operator. For example, in various embodiments, the method1200 may be partially or entirely performed by a controller, aprocessor, etc., or some other device having one or more processorstherein. The processor, e.g., processing circuit(s), chip(s), and/ormodule(s) implemented in hardware and/or software, and preferably havingat least one hardware component may be utilized in any device to performone or more steps of the method 1200. Illustrative processors include,but are not limited to, a central processing unit (CPU), an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), etc., combinations thereof, or any other suitable computingdevice known in the art. In one approach, the method is performed by thecontroller of a tape drive.

In operation 1202, a drive is instructed to move the tape to theapproximate linear position of the tape where the defect was detected,relative to a reader. Again, LPOS information stored when the defect wasdetected may be used to move the tape to the position. The drive movingthe tape may be a different drive than the one that detected the defect.In other approaches, the drive moving the tape may be the drive thatdetected the defect, and presumes said drive has at least one reader andis configured to detect the written signal burst, as will soon becomeapparent in the discussion of operation 1204. Using linear positioninformation allows the tape to be quickly moved to the approximatelocation of the defect.

In operation 1204, the drive is instructed to detect the written signalburst, and stop tape movement near or at the signal burst. The tape maybe moved more slowly for this operation than operation 1202. In someapproaches, operation 1202 may be omitted, and the tape simply read inoperation 1204 until the written signal burst is detected.

Assuming the first transition of the signal burst is aligned with thedefect, the first transition may be detected using conventionaltechniques, e.g., magnetic force microscopy, ferrofluid tape developing,etc.

At this point, the approximate location of the defect is identified, andtechniques such as AFM scanning, optical scanning, etc. may be used tosearch the tape surface for the defect. A section of the tape may besectioned and placed in the desired tool, physically and/or opticallymarked and unspooled for analysis, etc.

Typically, tape defects are less than 3 microns in diameter, and in maybe closer to 1 micron or less. A one-half-inch tape is approximately12,700 microns wide, and so the maximum diameter of the defect may beless than 1/5000^(th) the width of the tape, and more likely less than1/10000^(th) the width of the tape. It follows that searching usingtechniques having high enough resolution such as AFM to find the defectwill be extremely slow. Accordingly, some approaches use furtherrefinement to determine the approximate lateral location of the defect,thereby significantly reducing the search area on tape, which in turngreatly reduces the time required to find the defect.

In operation 1206, the approximate lateral position of the defect in thecross-track direction is determined. In one approach, the lateralposition may be correlated to the detector that detected the defect, andthe area on the tape that was aligned with that detector may beanalyzed. The granularity of the search area is thus dependent upon thewidth of the detector.

In a preferred embodiment, the search area is further reduced byanalyzing the detector structure that detected the defect, using anyknown technique, to determine the location of the material smeared bythe defect. Preferably, an optical technique is used to find the smear,optionally with machine vision, as optical techniques enable much morerapid scanning than scanning techniques such as AFM. FIG. 13 depicts adetector structure 802 having a smear 1302 of conductive materialpassing from the lower conductive layer 812, across the insulating layer814 onto the upper conductive layer 812, e.g., as caused by a defect ona tape passing in an upward direction across the detector structure 802.

Once the location of the smeared material is known, the distance in thecross track direction from that location to the projected laterallocation of some convenient known datum is then measured. Such datum maybe the edge of the servo pattern, an edge of a writer (e.g., the firstwriter that wrote), the edge of a servo reader, etc. Then thecorresponding area of the tape may be analyzed. This significantlyreduces the search area, and may reduce the search time to find thedefect to mere minutes or hours. Any known process of detecting thelocation of the smear may be used. Preferred approaches use opticaldetection to locate the smear. In one approach, dark field microscopymay be used to locate the smear. Other approaches include inspection viadifferential interference contrast (DIC) techniques, AFM, etc.

In operation 1208, a search for the defect is conducted using any knowntechnique, e.g., AFM. Once the defect is found, further operations maybe performed, such as identifying and storing characteristics of thedefect, sending the defect away for analysis, etc.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Moreover, a system according to various embodiments may include aprocessor and logic integrated with and/or executable by the processor,the logic being configured to perform one or more of the process stepsrecited herein. By integrated with, what is meant is that the processorhas logic embedded therewith as hardware logic, such as an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), etc. By executable by the processor, what is meant is that thelogic is hardware logic; software logic such as firmware, part of anoperating system, part of an application program; etc., or somecombination of hardware and software logic that is accessible by theprocessor and configured to cause the processor to perform somefunctionality upon execution by the processor. Software logic may bestored on local and/or remote memory of any memory type, as known in theart. Any processor known in the art may be used, such as a softwareprocessor module and/or a hardware processor such as an ASIC, a FPGA, acentral processing unit (CPU), an integrated circuit (IC), etc.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer.

The inventive concepts disclosed herein have been presented by way ofexample to illustrate the myriad features thereof in a plurality ofillustrative scenarios, embodiments, and/or implementations. It shouldbe appreciated that the concepts generally disclosed are to beconsidered as modular, and may be implemented in any combination,permutation, or synthesis thereof. In addition, any modification,alteration, or equivalent of the presently disclosed features,functions, and concepts that would be appreciated by a person havingordinary skill in the art upon reading the instant descriptions shouldalso be considered within the scope of this disclosure.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A computer program product comprising a computerreadable storage medium having program instructions embodied therewith,the program instructions executable by a controller to cause thecontroller to: monitor, by the controller, a resistance value of each ofa plurality of detector structures positioned in an array; and detect,by the controller, a change in a resistance value of at least one of thedetector structures, for identifying a defect on a magnetic medium,wherein each of the detector structures includes a pair of conductivelayers separated by an insulating material, with a proviso that none ofthe detector structures include an operable reader for reading data froma magnetic medium.
 2. The computer program product of claim 1, whereinthe program instructions are executable by a controller to cause thecontroller to: use, by the controller, a servo reader to determine aposition along a length of the magnetic medium that corresponds to anidentified defect.
 3. The computer program product of claim 1, whereinthe program instructions are executable by a controller to cause thecontroller to: cause, by the controller, a plurality of writetransducers to write in response to detecting the change in resistancevalue.
 4. The computer program product of claim 1, wherein a distanceseparating the conductive layers of each of the detector structures,measured in an intended direction of magnetic media travel, is in arange of from about 2 nm to about 10 nm.
 5. The computer program productof claim 1, wherein the insulating material is the only layer positionedbetween the conductive layers in each of the detector structures.
 6. Thecomputer program product of claim 1, wherein the program instructionsare executable by a controller to cause the controller to: cause, by thecontroller, at least one write transducer to write a signal burst on amagnetic medium at about a position of an identified defect along alength of the magnetic medium.
 7. The computer program product of claim1, wherein the program instructions are executable by a controller tocause the controller to: evaluate, by the controller, a number ofidentified defects per unit surface area of a magnetic tape to determinea quality of the magnetic tape.
 8. The computer program product of claim1, wherein a width of the array of detector structures is wider in across-track direction than an array of the at least one writetransducer.
 9. The computer program product of claim 1, wherein theinsulating material includes a laminate of layers.
 10. The computerprogram product of claim 1, wherein each of the detector structuresincludes a resistor associated therewith, wherein each resistor couplesthe respective pair of conductive layers together.
 11. Acomputer-implemented method, comprising: monitoring a resistance valueof each of a plurality of detector structures positioned in an array;and detecting a change in a resistance value of at least one of thedetector structures for identifying an approximate location of a defecton a magnetic medium, wherein each of the detector structures includes apair of conductive layers separated by an insulating material, with aproviso that none of the detector structures include an operable readerfor reading data from a magnetic medium.
 12. The computer-implementedmethod of claim 11, comprising: evaluating a number of identifieddefects per unit surface area of a magnetic tape to determine a qualityof the magnetic tape.
 13. The computer-implemented method of claim 11,wherein a distance separating the conductive layers of each of thedetector structures, measured in an intended direction of magnetic mediatravel, is in a range of from about 2 nm to about 10 nm.
 14. Thecomputer-implemented method of claim 11, wherein the insulating materialis the only layer positioned between the conductive layers in each ofthe detector structures.
 15. The computer-implemented method of claim11, wherein the insulating material includes a laminate of layers. 16.The computer-implemented method of claim 11, wherein each of thedetector structures includes a resistor associated therewith, whereineach resistor couples the respective pair of conductive layers together.